Recently, delustered electrocoat, especially delustered aluminum sash, has become popular, and many methods of delustering have been proposed.
As a conventional delustering method, it has been known that a delustering pigment such as silicate can be mixed into electrocoatings.
However, in this method the delustering pigment is liable to precipitate or to coagulate, so that stability of the coatings is poor, and also, a coat having a constant and even gloss and a high alkaline resistance is difficult to be obtained.
A method of using delustering paint containing a resin poor in compatibility is known. However, the paint lacks stability and washability, and additionally often causes uneven appearance.
A method of obtaining a delustered coat in which an electrocoated article is dipped into an aqueous solution of inorganic acid, organic acid or salts before baking has been known. In this method, the delustering effect is insufficient, because the solution is washed off (if the washing process is omitted, the coated surface becomes uneven due to drops of the solution which form on and fall from the hanger for the article or edge of the article when it is pulled from the solution).
Japanese Patent Publication (KOKAI) No. 9392/1981 discloses that the delustering is achieved by the application of electric current to an electrocoated article in an aqueous solution of salts. However, the method causes uneven appearance. and gives an insufficient 60.degree.-mirror reflectance, of less than 40.
Japanese Patent Publication (KOKAI) No. 54595/1980 discloses a method of delustering in which alternating electric current (A.C.) is applied on an electrocoated article in an aqueous solution of acid such as sulfonic acid, nitric acid, phosphoric acid, cresolsulfonic acid or p-toluene-sulfonic acid. However, the alternating electric current is essentially applied, which makes it difficult to control the gloss and gives rise to uneven appearance.